This invention relates to improvements in a pre-heating assembly to be used for pre-heating ingots each being transported to a melting furnace such as a pot of a casting apparatus for a die-casting operation, and more particularly, to a pre-heating apparatus having a special advantage for pre-heating a type of ingot having a spherical configuration like a ball.
Normally, the temperature inside a melting furnace such as a casting pot for use in a die-casting operation is maintained at an extremely high temperature. Such being the case, with respect to supply of ingots to such a high temperature condition, whenever the ingot is supplied to the pot without any pre-heating treatment thereof, the temperature of the molten metal contained in the pot is caused to be drastically decreased. In a continuous die-casting process, the variation of the temperature of the molten metal should be avoided. Thus, so long as such an operational defect as described above is not overcome, mass production of cast objects each having a constant high quality can hardly be achieved. Therefore, in order to prevent the occurrence of such an undesirable operational condition, the ingots are preferably pre-heated prior to their being supplied to the melting furnace. However, up to the present, such a pre-heating of the ingots has not been specifically taken into consideration in this field.
Simply, in order to accomplish such pre-heating of the ingots, the conventional die-casting process can be modified to include a separate pre-heating step by means of an independent pre-heating means. However, such an arrangement gives rise to another undesirable problem, i.e., an additional apparatus cost and more particularly, an additional manufacturing cost.
The inventors of the present invention have already purposed special ingots having a spherical configuration like a ball so that the ingot can be easily treated or handled at any station in the casting process, the details of which have been disclosed in Japanese Utility Model Application dated Dec. 29, 1976, or Japanese Laid Open Patent Application (Tokkaisho) 54-43835. The pre-heating asembly of the present invention is based upon the specific characteristics of the ingots described above as will be described hereinafter.